Toaster-cum-microwave oven

ABSTRACT

A toaster-cum-microwave oven includes a toasting chamber, a heating device, a temperature measuring device for measuring an inside temperature of the toasting chamber and producing a temperature signal indicating the measured inside temperature, a switching device for selectively cutting or allowing a power supply to the heating device, and a controlling device. The controlling device receives the temperature signal, determines an amount of heat required to cook the bread product, calculates an amount of heat supplied to the bread product by using the inside temperature of the toasting chamber, compares the supplied amount of heat with the required amount of heat, and controls the switching device to cut the power supply to the heating device if the supplied amount of heat is equal to or greater than the required amount of heat.

FIELD OF THE INVENTION

[0001] The present invention relates to a toaster-cum-microwave oven;and more particularly, to a toaster-cum-microwave oven which is capableof preventing over-toasting of a bread product caused by a residual heatfrom previous toast batches, toasting it to a user's desired degree.

BACKGROUND OF THE INVENTION

[0002] As disclosed in U.S. Pat. No. 6,539,840 entitled “MICROWAVE OVENHAING A TOASTER” and Japanese Patent No. 3271630 entitled “MICROWAVEOVEN WITH TOASTER”, a conventional toaster-cum-microwave (or microwaveoven/toaster combination) basically includes a microwave oven sectionfor cooking food in a heating chamber by means of microwave and atoaster section for toasting a bread product in a toasting chamber bymeans of Joule's heat.

[0003] Recently, such conventional toaster-cum-microwave oven is gainingpopularity for its versatility and convenience. Since, however, suchconventional toaster-cum-microwave oven is kind of an apparatus made bycombining a freestanding toaster with a microwave oven, it inherentlyhas the same kind of problem that a freestanding toaster also suffersfrom. That is, the bread product is over-toasted owing to residual heatleft in the toasting chamber from previous toast batches in case theconventional toaster-cum-microwave oven is operated consecutively in ashort interval. For example, the conventional toaster-cum-microwavetoasts slices of bread as medium, dark and burnt for color selection (ortoasting time selection) of light, medium and dark, respectively.

SUMMARY OF THE INVENTION

[0004] It is, therefore, an object of the present invention to provide atoaster-cum-microwave oven which is capable of preventing over-toastingof a bread product caused by a residual heat from previous toastbatches, toasting it to a user's desired degree.

[0005] In accordance with one aspect of the invention, there is provideda toaster-cum-microwave oven, including: a toasting chamber foraccommodating a bread product; a heating device which, when energized,supplies heat to the toasting chamber; a temperature measuring devicefor measuring an inside temperature of the toasting chamber andproducing a temperature signal indicating the measured insidetemperature; a switching device for selectively cutting or allowing apower supply to the heating device; and a controlling device having amemory, wherein the controlling device receives the temperature signalfrom the temperature measuring device, determines an amount of heatrequired to cook the bread product on a basis of data stored in thememory, calculates an amount of heat supplied to the bread product byusing the inside temperature of the toasting chamber, compares thesupplied amount of heat with the required amount of heat, and controlsthe switching device to cut the power supply to the heating device ifthe supplied amount of heat is equal to or greater than the requiredamount of heat.

[0006] In accordance with another aspect of the invention, there isprovided with a method for cooking a bread product in atoaster-cum-microwave oven which has a toasting chamber foraccommodating the bread product and a heating device which, whenenergized, supplies heat to the toasting chamber, the method includingthe steps of: (a) determining an amount of heat required to cook thebread product; (b) measuring a starting inside temperature of thetoasting chamber; (c) allowing a power supply to the heating device; (d)measuring an inside temperature of the toasting chamber; (e) calculatingan amount of heat supplied to the bread product by using the startinginside temperature and the inside temperature measured at the steps (b)and (d), respectively; (f) comparing the required amount of heat withthe supplied amount of heat; and (g) if the supplied amount of heat isequal to or greater than the required amount of heat, cutting the powersupply to the heating device.

[0007] In accordance with still another aspect of the invention, thereis provided with a toaster-cum-microwave oven, including: a toastingchamber for accommodating a bread product; a heating device which, whenenergized, supplies heat to the toasting chamber; a humidity measuringdevice for measuring an inside humidity of the toasting chamber andproducing a humidity signal indicating the measured inside humidity; aswitching device for selectively cutting or allowing a power supply tothe heating device; and a controlling device, wherein the controllingdevice receives the humidity signal, calculates a rate of change ofhumidity using the humidity signal, compares the rate of change ofhumidity with a predetermined value, and controls the switching deviceto cut the power supply to the heating device after a remaining cookingtime has lapsed if the rate of change of humidity is equal to or greaterthan the predetermined value.

[0008] In accordance with still another aspect of the invention, thereis provided with a method for cooking a bread product in atoaster-cum-microwave oven which has a toasting chamber foraccommodating the bread product and a heating device which, whenenergized, supplies heat to the toasting chamber, the method includingthe steps of: (a) measuring a starting inside humidity of the toastingchamber; (b) allowing a power supply to the heating device; (c)measuring an inside humidity of the toasting chamber; (d) calculating arate of change of humidity by using the starting inside humidity and theinside humidity measured at the steps (a) and (c); (e) comparing therate of change of humidity with a predetermined value; and (f) if therate of change of humidity is equal to or greater than the predeterminedvalue, cutting the power supply to the heating device after a remainingcooking time has lapsed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The above and other objects and features of the present inventionwill become apparent from the following description of preferredembodiments given in conjunction with the accompanying drawings, inwhich:

[0010]FIG. 1 presents a schematic diagram of a toaster-cum-microwaveoven in accordance with a first preferred embodiment of the presentinvention;

[0011]FIG. 2 is a flowchart for showing an operation of a controller ofthe toaster-cum-microwave of FIG. 1;

[0012]FIG. 3 depicts a schematic diagram of the toaster-cum-microwave inaccordance with the second preferred embodiment of the presentinvention;

[0013]FIG. 4 offers an exploded perspective view of a toaster section ofFIG. 3; and

[0014]FIG. 5 sets forth a flowchart for showing an operation of acontrolling device of the toaster-cum-microwave of FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Preferred embodiments of the present invention will now bedescribed in detail with reference to the accompanying drawings, whereinlike parts appearing FIGS. 1 to 6 are represented by like referencenumerals.

[0016] Referring to FIG. 1, there is presented a schematic diagramshowing construction of a toaster-cum-microwave oven in accordance witha first preferred embodiment of the present invention. Thetoaster-cum-microwave oven includes a microwave oven section for heatingfoodstuff by means of microwave and a toaster section for toastingslices of bread by means of Joule's heat. The microwave oven section isprovided with an instrument compartment 43, which has a magnetron (notshown) for generating the microwave, a high-voltage transformer (notshown) for supplying a high voltage to the magnetron, a cooling fan (notshown) for supplying cooling air and the like; and a heating chamber 46in which the foodstuff is heated by means of the microwave. The toastersection is provided with a toasting chamber 36 for accommodating theslices of bread; a heating device 39 which, when energized, suppliesheat to the toasting chamber 36; and a temperature measuring device 33which measures an inside temperature of the toasting chamber 36 andgenerates a temperature signal indicating the measured temperature.

[0017] Further, the toaster-cum-microwave oven includes an input device10 which receives a user's selection wherein the user's selectionrepresents which section is selected among the microwave oven sectionand the toaster section and/or a degree of browning of the slice ofbread, and produces a selection signal indicating such selection; and acontrolling device 20 which receives the temperature and the selectionsignal from the temperature measuring device 33 and the input device 10,respectively, and, according to these signals, controls a switchingdevice 23 which selectively cuts or allows a power supply to theinstrument compartment 43 of the microwave oven section and the heatingdevice 39 of the toaster section. A displaying device 14 shows signalsfrom the controlling device 20 to users in a readable form, and a powerunit 26 receives operation power, i.e., a.c. power from a conventionala.c. service 29, and supplies the operating power to the instrumentcompartment 43 and the heating device 39 through the switching device23, e.g., relay.

[0018] Referring to FIG. 2, there is illustrated a flowchart for showingan operation of the controlling device 20 of the toaster-cum-microwaveof FIG. 1. After the toaster-cum-microwave is activated, the controllingdevice 20 determines, at step S1, which section among the microwave ovensection and the toaster section is selected on the basis of theselection signal from the input device 10. If the microwave oven sectionis selected, the controlling device 20 makes the microwave oven sectionactivated. The operation of the microwave oven section is not a subjectmatter of the present invention, and so the description therefor isomitted. If the toaster section is selected, the controlling device 20receives, at step S1 a, signals as to the degree of browning of bread(e.g., light, medium or dark color) through the input device 10 anddetermines, at step S2, an amount of heat Qr required for toasting thebread. The determination of the amount of heat Qr is conducted by usingdata previously stored in a memory (not shown) of the controlling device20. Further, the user can input to the controlling device 20 through theinput device 10 more specific information about a bead product to becooked, such as, the number of slices of bread, bread type or thickness,and the controlling device 20 can use such information in determiningthe required amount of heat Qr.

[0019] Next, the controlling device 10 receives, at step S3, thetemperature signal indicating a starting inside temperature t0 of thetoasting chamber 36 from the temperature measuring device 33, andoperates, at step S4, the switching device 26 to supply a power supplyto the heating device 39. Then, the controlling device 10 receives, atstep S5, the temperature signal indicating an inside temperature tn(n=1, 2, 3, . . . ) of the toasting chamber in a predetermined interval,e.g., 2 seconds, and calculates, at step S6, an amount of heat suppliedto the slice of bread in the toasting chamber 36 by using t0 and tn.Next, at step S7, the controlling device 20 compares the required amountof heat Qr with the supplied amount of heat Qs. If the supplied amountof heat Qs is less than the required amount of heat Qr, the steps S5 andS6 are repeated. Meanwhile, if the supplied amount of heat Qs is equalto or greater than the required amount of heat Qr, the controllingdevice 20 operates, at step S8, the switching device 23 to cut the powersupply to the heating device 39 so that the heating device 39 turns off.

[0020] As described above, since the toaster-cum-microwave in accordancewith the first preferred embodiment of the present invention comparesthe amount of heat required for toasting, which is determined on thebasis of information input into the controlling device through theinputted device prior to the toasting, with the amount of heat suppliedto the slice of bread in the toasting chamber, which is calculated inthe course of the toasting by using the inside temperature of thetoasting chamber 36, and then operates the switching device to cut thepower supply to the heating device 39 if the supplied amount of heat isequal to or greater than the required amount of heat. Therefore, thebread product can be cooked or toasted to the user's desired degree.

[0021] Further, since the toaster-cum-microwave in accordance with thefirst preferred embodiment determines the ending time of the toasting byusing the required amount of heat Qr and the supplied amount of heat Qs,it does not suffer from a problem that the slices of bread are toastedimproperly owing to voltage deviation of domestic electricity supply.

[0022] Hereinafter, a toaster-cum-microwave oven in accordance with asecond preferred embodiment of the present invention will now bedescribed in detail, wherein like parts to those of the first preferredembodiment are referred to by like reference characters and thedescription therefor will not be repeated for simplicity.

[0023] Referring to FIG. 3, there is illustrated a schematic diagram ofthe toaster-cum-microwave in accordance with the second preferredembodiment of the present invention. The toaster-cum-microwave of thesecond preferred embodiment includes a humidity measuring device 35 formeasuring an inside humidity of the toasting chamber 36 instead of thetemperature measuring device 33 for measuring the inside temperature ofthe toasting chamber 36. The humidity measuring device 35 measures theinside humidity of the toasting chamber 36 and produces a humiditysignal indicating the measured inside humidity of the toasting chamber36. Electrically connected to the humidity measuring device 35 is acontrolling device 20 a, which receives the humidity signal therefrom.In addition, the controlling device 20 a receives a selection signalfrom the input device 10, which indicate a user's selection forrepresenting which section 13 selected among the microwave section andthe toaster section and/or the selection for the degree of browning ofbread.

[0024] Referring to FIG. 4, there is presented an exploded perspectiveview of the toaster section of FIG. 3. Disposed at an upper portion ofthe toasting chamber 36 is an upper plate 37 having a plurality of airopenings 38. Disposed above the upper plate 37 is a cover plate 34, atwhich the humidity measuring device 35 is installed. The plurality ofair openings 38 are formed in the upper plate 37 in such a manner thathumidity forming in the course of toasting the slices of bread risesupward uniformly. A probe section (not shown) of the humidity measuringdevice 35 is disposed on a lower surface of the cover plate 34 andmeasures humidity contained in air rising upward through the pluralityof air openings 38.

[0025] Further, the humidity forming in the course of toasting theslices of bread is exhausted to outside of the toast-cum-microwave ovenvia the heating chamber 46 of the microwave oven section, louvers formedin an outer casing (not shown) and the like. In addition, when thetoasting chamber 36 is opened for retrieval of the slices of bread, mostof the humidity in the toasting chamber 36 is exhausted therefrom.

[0026] Referring to FIG. 5, there is shown a flowchart for showing anoperation of the controlling device 20 a of the toaster-cum-microwave ofFIG. 3. At step S1, the controlling device 20 a determines whether themicrowave oven section or the toaster section is selected on the basisof the selection signal from the input device 10. If the microwave ovensection is selected, the controlling device 20 a transmits a propercontrol signal to the instrument compartment 43 to operate the microwaveoven section. Meanwhile, if the toaster section is selected, thecontrolling device 20 a receives the selection signal for the degree ofbrowning of bread from the input device 10 at step S2. The controllingdevice 20 a receives, at step S3, a starting humidity signal of thetoasting chamber 36 from the humidity measuring device 35, and controls,at step S4, the switching device 23 to allow the power supply to theheating device 39. Next, at step S5, the controlling device 20 areceives a humidity signal of the toasting chamber 36. Then, at step S6,the controlling device 20 a calculates the rate of change of humidityand determines whether the rate of change of humidity varies abruptly ornot, i.e., the controlling device 20 a compares the rate of change ofhumidity with the predetermined value. If the rate of change of humidityis equal to or greater than the predetermined value, the controllingdevice 20 a determines, at step S7, the remaining cooking time on thebasis of the selection signal for the degree of browning of breadinputted thereinto at the step S2, and controls the switching device 23to cut the power supply to the heating device 39 after the remainingcooking time has lapsed. For example, if the selection for the degree ofbrowning of bread is light, medium or dark, the remaining cooking timeis set 10 seconds, 30 seconds or 1 minute. Further, the user can inputto the controller 20 through the input device 10 more specificinformation about the slices of bread to be cooked or toasted, such as,the number of slices of bread, bread type or thickness, and thecontrolling device 20 can use such information in determining theremaining cooking time. Meanwhile, if the rate of change of humidity isless than the predetermined value, the controlling device 20 a repeatsthe steps S5, S6.

[0027] As described above, the remaining cooking time is determined atthe moment when the rate of change of humidity varies abruptly, i.e.,the moment when the color of the slices of bread in the toasting chamber36 is turned to brown. After this moment, the residual heat left in thetoasting chamber from previous toast batches seldom affects on toastingconditions, such as, the inside temperature of the toasting chamber.Therefore, the toaster-cum-microwave in accordance with the secondpreferred embodiment is capable of toasting the slices of bread to theuser's desired degree, and preventing over-toasting thereof frequentlyoccurring owing to the residual heat when the conventionaltoaster-cum-microwave is operated consecutively in a short interval.

[0028] Further, it should be noted that the concept of the presentinvention can be applied to a typical stand-alone toaster(or afreestanding toaster).

[0029] While the invention has been shown and described with respect tothe preferred embodiments, it will be understood by those skilled in theart that various changes and modifications may be made without departingfrom the spirit and scope of the invention as defined in the followingclaims.

What is claimed is:
 1. A toaster-cum-microwave oven, comprising: atoasting chamber for accommodating a bread product; a heating devicewhich, when energized, supplies heat to the toasting chamber; atemperature measuring device for measuring an inside temperature of thetoasting chamber and producing a temperature signal indicating themeasured inside temperature; a switching device for selectively cuttingor allowing a power supply to the heating device; and a controllingdevice having a memory, wherein the controlling device receives thetemperature signal from the temperature measuring device, determines anamount of heat required to cook the bread product on a basis of datastored in the memory, calculates an amount of heat supplied to the breadproduct by using the inside temperature of the toasting chamber,compares the supplied amount of heat with the required amount of heat,and controls the switching device to cut the power supply to the heatingdevice if the supplied amount of heat is equal to or greater than therequired amount of heat.
 2. The toaster-cum-microwave oven of claim 1,further comprising an input device for receiving a user's selection fora degree of browning of the bread product and generating a selectionsignal indicating the user's selection for the degree of browning of thebread product, wherein the controlling device receives and uses theselection signal in determining the required amount of heat.
 3. A methodfor cooking a bread product in a toaster-cum-microwave oven which has atoasting chamber for accommodating the bread product and a heatingdevice which, when energized, supplies heat to the toasting chamber, themethod comprising the steps of: (a) determining an amount of heatrequired to cook the bread product; (b) measuring a starting insidetemperature of the toasting chamber; (c) allowing a power supply to theheating device; (d) measuring an inside temperature of the toastingchamber; (e) calculating an amount of heat supplied to the bread productby using the starting inside temperature and the inside temperaturemeasured at the steps (b) and (d), respectively; (f) comparing therequired amount of heat with the supplied amount of heat; and (g) if thesupplied amount of heat is equal to or greater than the required amountof heat, cutting the power supply to the heating device.
 4. The methodof claim 3, before the step (a) further comprising the step of (h)selecting a degree of browning of the bread product, wherein therequired amount of heat in the step (a) is determined by using theselected degree of browning of the bread product.
 5. Atoaster-cum-microwave oven, comprising: a toasting chamber foraccommodating a bread product; a heating device which, when energized,supplies heat to the toasting chamber; a humidity measuring device formeasuring an inside humidity of the toasting chamber and producing ahumidity signal indicating the measured inside humidity; a switchingdevice for selectively cutting or allowing a power supply to the heatingdevice; and a controlling device, wherein the controlling devicereceives the humidity signal, calculates a rate of change of humidityusing the humidity signal, compares the rate of change of humidity witha predetermined value, and controls the switching device to cut thepower supply to the heating device after a remaining cooking time haslapsed if the rate of change of humidity is equal to or greater than thepredetermined value.
 6. The toaster-cum-microwave oven of claim 5,further comprising an input device for receiving a user's selection fora degree of browning of the bread product and producing a selectionsignal indicating the user's selection for the degree of browning of thebread product, wherein the controlling device receives and uses theselection signal in determining the remaining cooking time.
 7. Thetoaster-cum-microwave oven of claim 6, wherein the toasting chamberincludes: an upper plate in which a plurality of openings are formed;and a cover plate, disposed above the upper plate, at which the humiditymeasuring device is installed.
 8. A method for cooking a bread productin a toaster-cum-microwave oven which has a toasting chamber foraccommodating the bread product and a heating device which, whenenergized, supplies heat to the toasting chamber, the method comprisingthe steps of: (a) measuring a starring inside humidity of the toastingchamber; (b) allowing a power supply to the heating device; (c)measuring an inside humidity of the toasting chamber; (d) calculating arate of change of humidity by using the starting inside humidity and theinside humidity measured at the steps (a) and (c); (e) comparing therate of change of humidity with a predetermined value; and (f) if therate of change of humidity is equal to or greater than the predeterminedvalue, cutting the power supply to the heating device after a remainingcooking time has lapsed.
 9. The method of claim 8, before the step (a),further comprising the step of (g) selecting a degree of browning of thebread product, wherein the remaining cooking time is determined by usingthe selected degree of browning of the bread product.